The present invention relates generally to the preparation of cytology slides and, more particularly, to a device and associated method for preparing cytology slides.
Cytology slides are prepared to screen and diagnose cellular samples taken from, for example, tissue samples, samples from the uterine cervix, urine, sputum, blood, fine needle aspiration biopsy, urethral, bronchial brushings and washings, cerebral spinal fluid, and other body fluids. The reliability and efficacy of the screening methods of these slides are measured by their ability to diagnose infections, precancerous lesions or cancerous lesions while at the same time avoiding false positive or negative diagnosis. The reliability of these slides is a primary issue. Often, the results are not accurate or are unreadable. Thus, there is a constant effort to improve the reliability and efficacy in the preparation of cytology samples.
One of the most common uses of cytology slides is for screening and diagnosis of a cervical sample. Carcinoma of the cervix is one of the most common malignancies in women, causing nearly 5,000 deaths per year in the United States. Approximately 60% of these cases are associated with absent or deficient screening. Approximately 25% of the screening failures are the result of errors in cervical sampling or smear interpretation.1 
Screening for precancerous or cancerous changes of the uterine cervix traditionally involves microscopic assessment of cervical Papanicolaou smears, called Pap smears. This traditional method for screening requires scraping a woman""s cervix with a sampling device, such as a cotton applicator stick, spatula or brush, and smearing this sample onto a slide for review by a medical lab professional. The specimen is gently spread across a slide to evenly distribute the cell sample. The slide is then fixed, stained, and examined under a light microscope for cellular abnormalities.
In carrying out this operation, the portion of the cell sample that is smeared onto the slide may contain blood, mucus, inflammatory cells, and clumps of cells. Accurate interpretation of up to 40% of conventional Pap smears are compromised by the presence of blood, mucous, obscuring inflammatory cells, scant cellular material and air-drying artifacts.2 The presence of these contaminants can obscure many of the cells, causing important precancerous lesions to be missed when the slide is reviewed at the lab or, alternatively, making the entire slide unreadable.
One of the problems with the conventional Pap smear is how quickly the sample dries out once it is smeared on the slide. With a conventional Pap smear, the sample must be fixed immediately in order to avoid the drying out of the cells, which ruins the sample.
Another problem with the conventional Pap smear is the frequent inaccuracy of the test result. Common inaccuracies include both false positive and false negative Pap test results. A false positive Pap test occurs when a patient is told she has abnormal cells when the cells are actually normal. A false positive result may require a woman to undergo unnecessary and costly medical procedures. A false negative Pap test result occurs when a specimen is called normal, but the woman has a lesion. A false negative Pap test may delay the diagnosis and treatment of a precancerous or even a cancerous condition.
The conventional Pap smear has false negative rates ranging from 10-50%, with up to 90% of those false negatives due to limitations of sampling or slide preparation.3 To decrease false negative rates associated with interpretation error, re-screening a portion of the negative smear or recalling the patient for another sample is required.
Concern over the frequency of false-negative results of the traditional Pap smear has led to the development of a variety of other technologies or clinical strategies, such as liquid-based cytology systems, to improve Pap testing. For example, the Cytyc, Inc. (Marlborough, Mass.), ThinPrep(copyright) and the TriPath, Inc. (Burlington, N.C.), CytoRich(copyright) Pap test systems are two commercially available, FDA approved fluid-based methods used for the collection and preparation of cervicovaginal samples.
With the ThinPrep(copyright) system, a gynecologic sample is collected in the same manner as the conventional Pap test using a broom-type device or plastic spatula and endocervical brush combination, but rather than smearing the cytological sample directly onto a microscope slide, this method suspends the sample cells in a fixative solution (i.e. PreservCyt(copyright)). The ThinPrep(copyright) slide preparation system uses an automated apparatus called a Cytyc 2000(copyright) that involves filtration using vacuum pressure and positive pressure-transfer steps to prepare cytology slides.4 
With the CytoRich(copyright) slide preparation system, the gynecologic sample is also collected in the same manner as the conventional Pap test. Like the ThinPrep(copyright) system, the CytoRich(copyright) system also places the sample in a liquid medium for further purification prior to analysis. CytoRich(copyright) specimens are processed using two centrifugation steps through a gradient solution to separate the diagnostic cells from the interferring material. The cells are ultimately re-suspended in a final preparation that is applied to the slide using a special pipetting apparatus (Autocyte Prep System(copyright)) provided by the manufacturers (Tripath, Inc.). This transfer step can also be performed manually. Thereafter, a sample is placed on a slide and analyzed by cytology.
These new methods have demonstrated increased quality in the preparation of the sample, improved detection rates, and a reduced need for patients who must return for repeat smears. However, in both the ThinPrep(copyright) and the CytoRich(copyright) slide preparation systems, a time consuming and expensive procedure is followed to prepare a mono-dispersed layer of cells on a cytology slide.
Although each of these systems reduces significantly the false-negative rate of the traditional Pap smears, the health care market has been slow in adopting these systems because of their cost and preparation time compared to the conventional Pap smears.
The invention provides a device and a method of using the device that overcomes these problems. The device and associated method provide a better quality prepared cytology slide having a more even distribution of cells with less interference from debris than the conventional Pap method, while offering an easier, quicker and more economical procedure as compared to known liquid-based medium methods. Thus the device and associated method facilitate the preparation and screening process of cytology slides.
According to one embodiment, a device for facilitating the preparation of cytology slides comprises a first cover having an inside surface, a second cover having an inside surface and an interposed spine. The spine may be replaced by one or more hinges. The first and second cover are pivotably secured to the spine so as to be foldable into a book form capable of an open and closed position. An absorbent material is mounted on the inside surface of the first cover and a filter overlays the absorbent material. The cytology slide is removeably mounted to the inside surface of the second cover. The slide is positioned on the inside surface of the second cover to contact with the filter when the book-like device is in the closed position.
In another aspect, the invention is directed to a method of preparing cytology slides. The method comprises combining a cellular sample with a liquid-based medium to create a solution, mixing the solution, extracting the sample or an aliquot of the sample from the solution and providing a slide preparation device. The device comprises a first cover having an inside surface, a second cover having an inside surface and an interposed spine. The first and second cover are pivotably secured to the spine so as to be foldable into a book form. An absorbent material is mounted to the inside surface of the first cover and a filter overlays the absorbent material. A slide is removeably mounted to the inside of the second cover so that the filter contacts the slide when the device is in the closed position. The method further comprises applying the sample to the filter, closing the book form so that the filter containing the sample contacts the slide, and applying a pressure to the contact surface to effectively transfer the specimen to the slide. The range of pressures appropriate for the absorbent matter and the filter in the device is provided by the design of the device. In this way, a cytology slide containing an evenly distributed number of cells is prepared quickly and reliably.